This prospective controlled follow-up study was designed to examine the effects of adnexal torsion on long-term ovarian histology and radical scavenger (FRS) activity, and subsequent viability following the detorsion of twisted ischaemic adnexa, in a primate centre of a university clinic. Adnexal torsion/occlusion was created by twisting the adnexa three times and fixing on to the side wall or by applying vascular clips in cycling female rats at 70 days of age. Following an ischaemic period of 4 to 36 h, the twisted adnexas were surgically removed and fixed. In the second group of rats, following the above ischaemic periods, the torsion/occlusion were relieved by detwisting or removing the vascular clips. Then the animals were reperfused for a week and adnexas were extirpated. After both ischaemia and reperfusion, the removed adnexas were examined histologically and tissue concentrations of glutathione peroxidase, superoxide dismutase, catalase and glutathione were determined. Regardless of the ischaemia time, all the twisted adnexas were black-bluish in appearance. Despite the gross ischaemic-haemorrhagic features, histological sections revealed negligible changes, with intact ovarian structure similar to controls in 4-24 h groups. Though decreased compared with controls, the change in tissue concentrations of FRS was not significant in 4-24 h groups. Only the 36 h group showed prominent congestion on all sections and a significant decrease in all radical scavenger concentrations studied. While no longterm reperfusion injury was observed histologically in 4-24 h groups, the 36 h group ended with adnexal necrosis. Our findings support the importance of early diagnosis and conservative surgical management (detorsion) in adnexal torsion. Lack of histological changes and unimpaired FRS metabolism are consistent with the recent data that vascular compromise is caused by venous or lymphatic stasis in early torsion and that adnexal integrity is not correlated with gross ischaemic appearance, thus providing evidence of adnexal resistance against ischaemia.